Thermal glass transition beyond kinetics of a non-crystallizable glass-former

Philipp, Martine; Nies, Christophe; Ostermeyer, Martin; Possart, Wulff; Krüger, Jan

doi:10.1039/c7sm02359f

Cited by 18 publications

(9 citation statements)

References 34 publications

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“…As evidenced by equations 1 and 2 this measurement does not take into account the temperature modulation and considers only the temperature ramp (see Equations (1) and (2)). For that reason, these quantities (N MEAN , v, and β T ) have been regarded to account for the kinetic part of the transition in temperature ramp [26]. However as stated in the introduction, TMOR is also able to impose a sinusoidal temperature modulation that can yield the dynamic response of the sample.…”

Section: Resultsmentioning

confidence: 99%

Thermal Transitions of Cocoa Butter: A Novel Characterization Method by Temperature Modulation

Gouveia

Lixandrão

Tavares

et al. 2019

Foods

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For the first time, the novel experimental technique Temperature Modulated Optical Refractometry (TMOR) was employed for cocoa butter thermal transitions characterization. The average refractive index (NMEAN), the volume (v) change, and the volumetric expansion coefficient (βq) as well as the dynamic quantities β′ and β″ (real and imaginary volumetric expansion coefficient, respectively) were monitored during cooling and heating and compared to the heat flow curves obtained via the standard technique dynamic scanning calorimetry (DSC). The investigation of these quantities showed that TMOR analysis can yield not only thermal transitions temperatures that are comparable to DSC results, but also some new thermal events that are not detected by DSC. This outcome suggests that TMOR might provide some additional insights on cocoa butter melting and crystallization by means of frequency-dependent measurements due to temperature modulation. This new information that can be accessed during temperature ramps might provide a deeper insight into thermal behavior of fat-based foods, evidencing TMOR value as a tool for thermal transitions investigation.

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Section: Resultsmentioning

confidence: 99%

Thermal Transitions of Cocoa Butter: A Novel Characterization Method by Temperature Modulation

Gouveia

Lixandrão

Tavares

et al. 2019

Foods

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show abstract

“…Glasses subjected to extremely long annealing would also present a decoupling. In this case, much longer time scales are required to allow the observation of a significant separation between vitrification kinetics and the -relaxation for bulky polymeric specimens, e.g., when the liquid is quasi-static cooled with a rate of ∼10 −4 K/s (49).…”

Section: Downloaded Frommentioning

confidence: 99%

Vitrification decoupling from α-relaxation in a metallic glass

et al. 2020

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Understanding how glasses form, the so-called vitrification, remains a major challenge in materials science. Here, we study vitrification kinetics, in terms of the limiting fictive temperature, and atomic mobility related to the α-relaxation of an Au-based bulk metallic glass former by fast scanning calorimetry. We show that the time scale of the α-relaxation exhibits super-Arrhenius temperature dependence typical of fragile liquids. In contrast, vitrification kinetics displays milder temperature dependence at moderate undercooling, and thereby, vitrification takes place at temperatures lower than those associated to the α-relaxation. This finding challenges the paradigmatic view based on a one-to-one correlation between vitrification, leading to the glass transition, and the α-relaxation. We provide arguments that at moderate to deep undercooling, other atomic motions, which are not involved in the α-relaxation and that originate from the heterogeneous dynamics in metallic glasses, contribute to vitrification. Implications from the viewpoint of glasses fundamental properties are discussed.

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“…However, very recently an interesting work on PVAc extended the investigation of the molecular mobility and vitrification kinetics to time scales of the order of 10 4 sec. 75 Specifically, the frequency dependent complex coefficient of thermal expansion, that is, the linear thermal susceptibility, was characterized measuring the volume variation to a sinusoidal temperature variation with frequencies way below the sub-Hz regime. At the same time, and in the same sample, vitrification kinetics was characterized following the total coefficient of thermal expansion on cooling at rates as small as several mK:min À1 .…”

Section: Complex Vitrification Behaviormentioning

confidence: 99%

Physical aging and vitrification in polymers and other glasses: Complex behavior and size effects

Cangialosi

2024

Journal of Polymer Science

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The paradigmatic view on the transformation of a supercooled liquid into a glass, so‐called vitrification or glass transition, and the subsequent time evolution of the non‐equilibrium glass, addressed as physical aging, relies on the exclusive role of the main relaxation with super‐Arrhenius temperature dependence. The aim of the present review is to carefully scrutinize the wealth of recent experimental results, above all in polymeric glasses, showing the relevance of other relaxational mechanisms in both vitrification and physical aging. While the relaxation bears dominant role in both phenomena in proximity of the glass transition temperature, , a broad view on a much wider temperature range indicates that vitrification and physical aging are mediated by non‐ mechanisms of equilibration. This review also shows that a reduction of the typical time scale of equilibration can be achieved in glasses with large free interface, namely with reduced sample size. In this way, fast non‐ mechanisms of equilibration can be exploited to convey glasses to low energy states in experimentally feasible time scales, thereby attaining information on the existence of the so‐called “ideal glass” in small sized samples.

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Thermal glass transition beyond kinetics of a non-crystallizable glass-former

Cited by 18 publications

References 34 publications

Thermal Transitions of Cocoa Butter: A Novel Characterization Method by Temperature Modulation

Thermal Transitions of Cocoa Butter: A Novel Characterization Method by Temperature Modulation

Vitrification decoupling from α-relaxation in a metallic glass

Physical aging and vitrification in polymers and other glasses: Complex behavior and size effects

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